Resistor alloy, component produced therefrom and production method therefor

ABSTRACT

The invention relates to a resistor alloy ( 3 ) for an electrical resistor, in particular for a low-resistance current-measuring resistor, having a copper constituent, a manganese constituent and a nickel constituent. According to the invention, the manganese constituent has a mass fraction of 23% to 28%, while the nickel constituent has a mass fraction of 9% to 13%. The mass fractions of the alloy constituents are adjusted to one another in such a manner that, compared to copper, the resistor alloy ( 3 ) has a low thermal electromotive force at 20° C. of less than ±1 μν/K. The invention furthermore comprises a component made from such a resistor alloy and a production method therefor.

The invention relates to a resistance alloy for an electrical resistor,in particular for a low-ohm current-measuring resistor. The inventionfurther includes a component produced therefrom and a correspondingproduction method.

Copper-manganese-nickel alloys have already been in use for a long timeas materials for precision resistors, in particular for low-ohmcurrent-measuring resistors (“shunts”). An example of such acopper-manganese-nickel alloy is the resistance alloy marketed by theapplicant under the trade name Manganin® (e.g. Cu₈₄Ni₄Mn₁₂) with a massfraction of copper of 82-84%, a mass fraction of nickel of 2-4% and amass fraction of manganese of 12-15%. The known copper-manganese-nickelalloys satisfy all requirements for resistance alloys for precisionresistors, such as, for example, a low temperature coefficient of thespecific electrical resistance, a low thermal electromotive forceagainst copper and a high stability of the electrical resistance overtime. In addition, the known copper-manganese-nickel alloys have goodtechnological properties, in particular good working properties,allowing such copper-manganese-nickel alloys to be worked to form wires,ribbons, foils and resistor components. A disadvantage of the knowncopper-manganese-nickel alloys is, however, the limitation to relativelylow specific electrical resistances of not more than 0.5 (Ω·mm²)/m.

For higher specific electrical resistances, nickel-chromium alloys, forexample, are known, but these likewise exhibit various disadvantages. Onthe one hand, nickel-chromium alloys are mostly substantially moreexpensive than copper-manganese-nickel alloys. On the other hand,nickel-chromium alloys are more difficult to handle in many respectsfrom the production point of view. For example, the hot workability ofnickel-chromium alloys is relatively poor, and complex heat treatmentprocesses are necessary in order to establish specific electro-physicalmaterial properties. In addition, the working temperatures in themelting process are about 500K higher in the case of nickel-chromiumalloys than in the case of copper-manganese-nickel alloys, which leadsto higher energy costs and material wear of the working equipment.Moreover, the good acid resistance of nickel-chromium alloys, which isotherwise desirable, gives rise to major problems in the production ofresistor structures by etching and makes the removal by pickling ofoxides caused by heat treatment a complex and non-hazardousmanufacturing step.

Also known is the copper-manganese-nickel-aluminum alloy 29-5-1, whichhas a specific electrical resistance of 1 (Ω mm²)/m and therebysatisfies the requirement for a low temperature coefficient of thespecific electrical resistance. However, this resistance alloy has ahigh thermal electromotive force against copper at 20° C. of +3 μV/K,resulting in high fault currents which render this alloy unsuitable forprecise measurement applications.

In relation to the prior art, reference is further to be made to DE 1092 218 B, U.S. Pat. No. 3,985,589, JP 62202038 A and EP 1 264 906 A1.

Finally, DE 1 033 423 B discloses a resistance alloy of the generictype. However, this known resistance alloy has the disadvantage of arelatively high, in terms of amount, thermal electromotive force againstcopper of −2 μV/K.

Accordingly, the object underlying the invention is to provide acorrespondingly improved resistance alloy based oncopper-manganese-nickel, which resistance alloy has as high a specificelectrical resistance as possible, a low thermal electromotive forceagainst copper, a low temperature coefficient of the electricalresistance, and a high stability of the specific electrical resistanceover time, and which combines these properties with the goodtechnological properties (e.g. workability) described at the beginningof the known copper-manganese-nickel alloys.

This object is achieved by a resistance alloy according to the inventionaccording to the main claim.

The resistance alloy according to the invention firstly has, inconformity with the known copper-manganese-nickel alloys mentioned atthe beginning, a copper constituent, a manganese constituent and anickel constituent. The invention is distinguished by the fact that themanganese constituent has a mass fraction of from 23% to 28%, while thenickel constituent has a mass fraction of from 9% to 13%. It has beenshown in practice that such a resistance alloy based oncopper-manganese-nickel satisfies the requirements described above.

The mass fractions of the various alloying constituents are so matchedto one another that the resistance alloy according to the invention hasa low thermal electromotive force against copper which at 20° C. is lessthan ±1 μV/K, ±0.5 μV/K or even less than ±0.3 μV/K.

The mass fraction of the manganese constituent can be, for example, inthe range of 24%-27%, 25%-26%, 23%-25%, 23%-26%, 23%-27%, 24%-28%,25%-28%, 26%-28% or 27%-28%. A mass fraction of the manganeseconstituent of 24.5%-25.5% is particularly advantageous.

The mass fraction of the nickel constituent, on the other hand, can be,for example, in the range of 9%-12%, 9%-11%, 9%-10%, 10%-13%, 11%-13%,12%-13%, 10%-12% or 11%-12%.

Moreover, it has been shown that an additional tin constituent with amass fraction of up to 3% can contribute towards improving thetemperature stability of the specific electrical resistance. Theresistance alloy according to the invention therefore preferably alsohas a tin constituent with a mass fraction of up to 3%.

Furthermore, it has been shown in practice that an additional siliconconstituent with a mass fraction of up to 1% likewise contributestowards improving the temperature stability of the specific electricalresistance. The resistance alloy according to the invention cantherefore have, in addition to the tin constituent or instead of the tinconstituent, a silicon constituent with a mass fraction of up to 1%.

It has further been shown in practice that an additional magnesiumconstituent with a mass fraction of up to 0.3% contributes towardsavoiding embrittlement as a result of precipitation hardening effects.The resistance alloy according to the invention can therefore also have,in addition to the tin constituent and/or the silicon constituent orinstead of those constituents, a magnesium constituent with a massfraction of up to 0.3%.

A preferred embodiment of a resistance alloy according to the inventionis Cu₆₅Ni₁₀Mn₂₅ with a mass fraction of copper of 65%, a mass fractionof nickel of 10% and a mass fraction of manganese of 25%.

Another embodiment of a resistance alloy according to the invention isCu64Ni10Mn25Sn1 with a mass fraction of copper of 64%, a mass fractionof nickel of 10%, a mass fraction of manganese of 25% and a massfraction of tin of 1%. The mass fraction of tin can, however, also besmaller, which is then balanced by a correspondingly higher massfraction of copper.

A further embodiment of a resistance alloy according to the invention isCu₆₂Ni₁₁Mn₂₇ with a mass fraction of copper of 62%, a mass fraction ofnickel of 11% and a mass fraction of manganese of 27%.

A further embodiment of a resistance alloy according to the invention isCu₆₁Ni₁₁Mn₂₇Sn₁ with a mass fraction of copper of 61%, a mass fractionof manganese of 27%, a mass fraction of nickel of 11% and a massfraction of tin of 1%. The mass fraction of tin can also be smaller,which is balanced by a correspondingly higher mass fraction of copper.

In the resistance alloy according to the invention, the specificelectrical resistance is preferably in the range of from 0.5 (Ω·mm2)/mto 2 (Ω·mm2)/m.

Furthermore, the specific electrical resistance of the resistance alloyaccording to the invention preferably has a high stability over timewith a relative change of less than ±0.5% or ±0.25%, in particularwithin a period of 3000 hours and at a temperature of at least +140° C.,the higher temperature of at least +140° C. accelerating the ageingprocess.

In addition, it is to be mentioned that the resistance alloy accordingto the invention preferably has a low thermal electromotive forceagainst copper, which at 20° C. is preferably less than ±1 μV/K, ±0.5μV/K or even less than ±0.3 μV/K.

Furthermore, the specific electrical resistance is relativelytemperature-constant with a low temperature coefficient of preferablyless than ±50·10⁻⁶ K⁻¹, ±35·10⁻⁶ K⁻¹, ±30·10⁻⁶ K⁻¹ or ±20·10⁻⁶ K⁻¹, inparticular in a temperature range of from +20° C. to +60° C.

With regard to the electrical properties of the resistance alloyaccording to the invention, it is further to be mentioned that theresistance alloy has a resistance/temperature curve, which shows therelative change in resistance in dependence on the temperature, theresistance/temperature curve having a second zero-crossing whichpreferably occurs at a temperature of more than +20° C., +30° C. or +40°C. and/or at a temperature of less than +110° C., +100° C. or +90° C.

With regard to the mechanical properties of the resistance alloyaccording to the invention, mention is to be made of a mechanicaltensile strength of at least 500 MPa, 550 MPa or 580 MPa.

In addition, the resistance alloy according to the invention preferablyhas a yield strength of at least 150 MPa, 200 MPa or 260 MPa, while thebreaking elongation is preferably greater than 30%, 35%, 40% or even45%.

With regard to the technological properties of the resistance alloyaccording to the invention, it is to be mentioned that the resistancealloy is preferably capable of being soft-soldered and/or hard-soldered.

In addition, the resistance alloy according to the invention ispreferably very readily workable, which manifests itself in the case ofwire drawing in a logarithmic deformation degree of at least φ=−4.6.

The resistance alloy according to the invention can be produced invarious forms of delivery, such as, for example, in the form of a wire(e.g. round wire, flat wire), in the form of a ribbon, in the form of asheet, in the form of a rod, in the form of a tube or in the form of afoil. However, the invention is not limited in respect of the forms ofdelivery to the forms of delivery mentioned above.

The invention additionally also includes an electrical or electroniccomponent having a resistor element made from the resistance alloyaccording to the invention. For example, it can be a resistor, inparticular a low-ohm current-measuring resistor, as is known per se fromEP 0 605 800 A1, for example.

Finally, the invention also includes a corresponding production method,as already follows from the above description of the resistance alloyaccording to the invention.

Within the scope of the production method according to the invention,the resistance alloy can be subjected to an artificial thermal ageingprocess, wherein the resistance alloy is heated from a startingtemperature to an ageing temperature. This process can be repeatedseveral times within the scope of the ageing process, the resistancealloy repeatedly being periodically heated to the ageing temperature andcooled to the starting temperature again. The ageing temperature can be,for example, in the range of from +80° C. to +300° C., while thestarting temperature is preferably less than +30° C. or +20° C.

Other advantageous further developments of the invention arecharacterized in the dependent claims or will be explained in greaterdetail hereinbelow with reference to the figures, together with thedescription of the preferred embodiments of the invention. In thefigures:

FIG. 1: is a phase diagram for a copper-manganese-nickel alloy, theregion according to the invention being plotted in the phase diagram,

FIG. 2: shows an example of a construction of a current-measuringresistor according to the invention having a resistor element made fromthe resistance alloy according to the invention,

FIG. 3: is a diagram illustrating the temperature dependence of thespecific electrical resistance in the case of different embodiments ofthe resistance alloy according to the invention, and

FIG. 4: is a diagram illustrating the long-term stability of theresistance alloy according to the invention.

FIG. 1 shows a phase diagram of a copper-manganese-nickel alloy, themass fraction of copper being shown on the top left axis, while the massfraction of nickel is shown on the top right axis. The mass fraction ofmanganese, on the other hand, is shown on the bottom axis.

On the one hand, the phase diagram shows in hatched form a zone 1 inwhich the resistance alloy tends to precipitation hardening.

On the other hand, the phase diagram shows a line 2 which is designatedα=0, the temperature coefficient of the resistance alloy on this linebeing equal to zero, that is to say the resistance alloy has on thisline a specific electrical resistance which is independent of thetemperature.

Finally, the phase diagram also shows a region 3 which characterizes theresistance alloy according to the invention, the mass fraction ofmanganese in the region 3 being from 23% to 28%, while the mass fractionof nickel in the region 3 is from 9% to 13%.

FIG. 2 shows a simplified perspective view of a current-measuringresistor 4 according to the invention, as is already known per se fromEP 0 605 800 A1 so that, in order to avoid repetition, reference is madeto that patent application, the content of which is to be incorporatedin its entirety in the present description.

The current-measuring resistor 4 consists substantially of twoplate-like connecting parts 5, 6 of copper and, arranged therebetween, aresistor element 7 made from the resistance alloy according to theinvention, which alloy can be, for example, Cu₆₅Ni₁₀Mn₂₅.

FIG. 3 shows the temperature-dependent development of the relativeresistance change DR/R20 in dependence on the temperature. It is alsoapparent therefrom that the various exemplary resistance alloys eachhave a second zero-crossing 8, 9 or 10, the zero-crossing 8 occurringapproximately at a temperature T_(ZERO1)=43° C., while the zero-crossing9 occurs approximately at a temperature T_(ZERO2)=75° C. Thezero-crossing 10, on the other hand, occurs approximately at atemperature of T_(ZERO3)=82° C.

Finally, FIG. 4 shows the long-term stability of the resistance alloyaccording to the invention. It is apparent therefrom that the relativeresistance change dR over a period of 3000 hours is substantially lessthan 0.25%.

The invention is not limited to the preferred embodiments describedabove. Rather, a plurality of variants and modifications are possiblewhich likewise make use of the inventive concept and therefore fallwithin the scope of protection. Moreover, the invention also claimsprotection for the subject-matter and features of the dependent claimsindependently of the claims on which they are dependent, that is to say,for example, also without the characterizing feature of the main claim.

LIST OF REFERENCE NUMERALS

-   1 Zone of precipitation hardening-   2 Line with α=0 (temperature stability)-   3 Alloying region according to the invention-   4 Current-measuring resistor-   5 Connecting part-   6 Connecting part-   7 Resistor element-   8 Second zero-crossing-   9 Second zero-crossing-   10 Second zero-crossing

1-10. (canceled)
 11. A resistance alloy for an electrical resistorcomprising: a) a copper constituent, b) a manganese constituent with amass fraction of from 23% to 28%, and c) a nickel constituent with amass fraction of from 9% to 13%, d) wherein the mass fractions of themanganese constituent and of the nickel constituent are effective toprovide the resistance alloy with a low thermal electromotive forceagainst copper at 20° C. of less than ±1 μV/K.
 12. The resistance alloyaccording to claim 11, further comprising a tin constituent with a massfraction of up to 3% for improving a temperature stability of a specificelectrical resistance of the resistance alloy.
 13. The resistance alloyaccording to claim 11, further comprising a silicon constituent with amass fraction of up to 1% for improving a temperature stability of aspecific electrical resistance of the resistance alloy.
 14. Theresistance alloy according to claim 11, further comprising a magnesiumconstituent with a mass fraction of up to 0.3% for avoidingembrittlement as a result of precipitation hardening effects.
 15. Theresistance alloy according to claim 11, wherein a mass fraction of thecopper constituent is substantially 65% and the mass fraction of thenickel constituent is substantially 10% and the mass fraction of themanganese constituent is substantially 25%.
 16. The resistance alloyaccording to claim 12, wherein the mass fraction of the nickelconstituent is substantially 10% and the mass fraction of the manganeseconstituent is substantially 25% and the mass fraction of the tinconstituent is up to 1% and a mass fraction of the copper constituentsubstantially accounts for the remainder.
 17. The resistance alloyaccording to claim 11, wherein a mass fraction of the copper constituentis substantially 62% and the mass fraction of the nickel constituent issubstantially 11% and the mass fraction of the manganese constituent issubstantially 27%.
 18. The resistance alloy according to claim 12,wherein the mass fraction of the nickel constituent is substantially 11%and the mass fraction of the manganese constituent is substantially 27%and the mass fraction of the tin constituent is up to 1% and a massfraction of the copper constituent substantially accounts for aremainder thereof.
 19. The resistance alloy according to claim 11,further comprising a specific electrical resistance which is greaterthan 0.5 (Ω·mm²)/m and less than 2.0 (Ω·mm²)/m.
 20. The resistance alloyaccording to claim 11, further comprising a specific electricalresistance having a high stability over time with a relative change ofless than ±0.5% within a period of 3000 hours.
 21. The resistance alloyaccording to claim 11, further comprising a low thermal electromotiveforce against copper at 20° C. of less than ±0.5 μV/K.
 22. Theresistance alloy according to claim 11, further comprising a specificelectrical resistance having a low temperature coefficient of less than±50·10⁻⁶ K⁻¹ in a temperature range of from +20° C. to +60° C.
 23. Theresistance alloy according to claim 11, further comprising aresistance/temperature curve which shows relative resistance change independence on temperature, the resistance/temperature curve having asecond zero-crossing which occurs at a temperature of more than +20° C.and at less than +110° C.
 24. The resistance alloy according to claim11, further comprising a) a mechanical tensile strength of at least 500MPa, and b) a yield strength of at least 150 MPa, and c) a breakingelongation of at least 30%.
 25. The resistance alloy according to claim11, wherein a) the resistance alloy is capable of being soldered, and b)the resistance alloy is so readily workable that it achieves alogarithmic deformation degree of at least φ=−4.6 in a case of wiredrawing.
 26. The resistance alloy according to claim 11, being providedin a form selected from the group consisting of a wire, a ribbon, asheet, a rod, a tube and a foil.
 27. A resistor having a resistorelement made from a resistance alloy according to claim
 11. 28. Aproduction method for producing a resistance alloy for an electricalresistor comprising the following steps: a) providing a copperconstituent, b) providing a manganese constituent with a mass fractionof from 23% to 28% and c) providing a nickel constituent with a massfraction of from 9% to 13% are alloyed to form the resistance alloy, andd) combining the copper constituent, the manganese constituent and thenickel constituent to provide the resistance alloy, e) wherein the massfractions of the manganese constituent and of the nickel constituent areso chosen that the resistance alloy has a low thermal electromotiveforce against copper at 20° C. of less than ±1 μV/K.
 29. The productionmethod according to claim 28, wherein the resistance alloy is subjectedto an artificial thermal ageing process, wherein the resistance alloy isheated from a starting temperature to an ageing temperature.
 30. Theproduction method according to claim 28, wherein the artificial thermalageing process further comprises repeatedly periodically heating theresistance alloy to the ageing temperature and cooling to the startingtemperature again.
 31. The production method according to claim 30,wherein the ageing temperature is greater than +80° C.
 32. Theproduction method according to claim 31, wherein the startingtemperature is less than +30° C.